1. Field of the Invention
The present invention relates to a semiconductor device and a method of manufacturing the semiconductor device.
2. Description of the Related Art
A ferroelectric memory using a ferroelectric film such as a Pb(ZrxTi1-x)O3 film (a PZT film) for a dielectric film of a capacitor, i.e., a FeRAM (ferroelectric random access memory) has recently been developed.
The ferroelectric memory has a problem that a capacitor decreases in characteristics and reliability because of a diffusion of hydrogen into the capacitor. For example, a step of patterning a capacitor film by RIE and a step of forming an interlayer insulating film by CVD after forming the capacitor are carried out in a gaseous atmosphere containing hydrogen. A hydrogen barrier film therefore needs to prevent hydrogen from diffusing. A conventional ferroelectric memory had two problems because no adequate measures were taken against a diffusion of hydrogen.
The first problem is as follows. A silicon nitride film is known as one hydrogen barrier film (see Jpn. Pat. Appln. KOKAI Publication No. 2001-15698, for example). Conventionally a silicon nitride film was formed in a gaseous atmosphere containing hydrogen such as SiH4 and thus a diffusion of the hydrogen caused a problem.
The second problem is as follows. Conventionally a hydrogen barrier film was formed chiefly only around a capacitor. To form a hydrogen barrier film only around a capacitor is not always adequate measures against a diffusion of hydrogen because the hydrogen barrier film cannot shut off the hydrogen completely. A ferroelectric memory generally has a multilevel interconnect structure that is obtained by repeatedly forming an interlayer insulating film and a wiring layer after a capacitor is formed. Since most interlayer insulating films are formed in a gaseous atmosphere containing hydrogen, it is necessary to take measures to effectively prevent the hydrogen from diffusing. Jpn. Pat. Appln. KOKAI Publication No. 2001-15703 discloses a structure in which a hydrogen barrier film is formed between interlayer insulating films. However, the structure of the Publication aims at resolving a problem with hydrogen annealing and takes into no consideration a diffusion of hydrogen occurring when an interlayer insulating film is formed in a multilevel interconnect structure. It is thus difficult to exactly prevent a diffusion of hydrogen due to the formation of interlayer insulating films.
As described above, conventionally, no adequate measures were taken against a diffusion of hydrogen. No capacitors that improved in characteristics and reliability were difficult to achieve.